The present invention relates to a method for the production of organic light emitting illuminants, in particular organic light emitting diodes.
Organic light emitting illuminants, in particular organic light emitting diodes (OLEDs), are currently already used in many areas of consumer electronics, for example in display applications, and are also regarded as a future technology in the lighting sector. An OLED structure contains one or more organic light emitting layers (EML) arranged between two electrodes, for example a cathode and an anode on a substrate. Since, for the OLED structure, the mobility and thus the current density differ for electrons and holes, since the mobility of the holes in organic semiconductors in comparison is two orders of magnitude greater than the mobility of the electrons, an OLED usually additionally has two layers, a hole transport layer (HTL) and an electron transport layer (ETL), the task of which is to transport holes and electrons into the emission zone.
FIG. 1 illustrates a schematic construction of an OLED known from the prior art. It consists of a substrate 100, on which an optionally smoothing layer 101, an anode layer 102, a hole transport layer 103 (HTL), at least one emission layer 104 (EML), an electron transport layer 105 (ETL) and a cathode layer 106 have been deposited in sequence. In FIG. 1, the emission layer 104 consists of three separate emission layers, which each emit light individually in different colors (e.g. red, green, blue) and can generate white light.
The organic light emitting layers emit light if a voltage is applied between anode and cathode. The applied voltage at the electrodes results in charge carrier injection in the organic material. This leads to charge carrier transport into the emission zone, where a recombination of the charge carriers takes place and the light emission is subsequently brought about.
In order to enable an electrical contact-connection of cathode and anode and also a current flowing through the emissive layers, the individual layers are not constructed over the whole area, but rather are deposited in a patterned fashion. One possibility for patterned deposition is disclosed by the document U.S. Pat. No. 7,049,757, which discloses a coating by means of shadow masks concomitantly guided with the substrate. Furthermore, the prior art in the document US 2005/0236975 A1 describes a patterning method in which the deposited layer is ablated by means of a laser. A further possibility for patterned deposition is lithographic/wet-chemical patterning, in particular for patterning the first bottom electrode applied on the substrate. These known methods have the disadvantage of complex handling of the concomitantly moving shadow masks and are unsuitable for the coating of flexible continuous substrates in the roll-to-roll method.